Certain mobile devices, such as, for example, location-aware mobile devices, cellular telephones, smart telephones, tablets, or the like may assist users in estimating their geographic location by providing suitable or desired navigation or positioning information obtained or gathered from various systems. One such system may include, for example, a satellite positioning system (SPS), such as the Global Positioning System (GPS) or other like Global Navigation Satellite Systems (GNSS) comprising a number of Earth-orbiting satellites or space vehicles (SVs) capable of transmitting wireless signals to and receiving such signals from one or more suitable wireless transmitters or receivers, terrestrial or otherwise.
In an indoor environment, mobile devices may be unable to reliably receive or acquire requisite wireless signals to facilitate or support one or more position estimation techniques, for example, so as to enable location or navigation services. For example, in certain venues, signals from SVs or other wireless transmitters may be attenuated or otherwise affected in some manner (e.g., insufficient, weak, fragmentary, etc.), which may preclude their use in a given position estimation technique.
Accordingly, in an indoor or like environment, different techniques may be employed, for example, to enable navigation or location services. For example, a position of a mobile communication device may be estimated using an Institute of Electrical and Electronics Engineers (IEEE) wireless local access network (WLAN) standard 802.11 heat map signature matching technique, for example, in which characteristics of 802.11 WLAN wireless signals or signal signatures received at a mobile device are compared with expected signatures of such characteristics stored as heat map values in a database, wherein the individual signal signatures stored in the database are associated with particular locations. The heat map may comprise a grid of points, which may be associated with a local or global coordinate system and may be laid over or mapped to a floor plan of a venue at substantially uniform spacing. Observed characteristics of received 802.11 WLAN wireless signals may be expressed, for example, by one or more real values in relation to every detectable 802.11 WLAN access point, such as received signal strength indicator (RSSI), or round-trip time (RTT), etc. By finding a signature in a database that most closely matches characteristics exhibited by 802.11 WLAN wireless signals received at a mobile device, a location associated with a matching signature may be used as an estimated location of a mobile device. It should be appreciated that other positioning techniques including sequential filtering methods such as Particle filters, extended Kalman filters, and unscented Kalman filters, etc., are also sometimes utilized.
In one implementation, a mobile device downloads the database, or part thereof, in the form of assistance data (AD) from a server, and performs heat map signature matching locally to obtain an estimated location.